The present invention relates to a process for the separation of components of aqueous liquids containing salts and nonionic, organic compounds. In particular, the invention is a process for separating the components of animal fluids to recover high purity products.
Often, the production of animal products, such as meats, cheeses and the like, have associated therewith significant amounts of waste streams. For example, a major by-product in the cheese industry is whey. Blood and other protein-containing waste streams are often by-products of other animal processing industries. It has been found that such waste streams, in particular milk whey, possess significant quantities of useful proteins, natural sugars, salts and other useful materials. In fact, the protein found in such waste streams is often of very high quality.
Unfortunately, such useful products are often discarded rather than recovered. However, due to increasing concern about the disposal of such waste streams, and the development of end uses for the proteins and other materials found therein, there has recently developed a greater interest in recovering the components of those animal waste streams.
Ion exchange techniques have been employed to recover desirable proteins from animal waste streams. For example, in British Pat. Nos. 1,387,265; 1,436,547 and 1,585,111 is described the use of certain cellulosic ion exchangers to remove proteins from whey, blood, and the like. Unfortunately, the physical form of these cellulosic materials is not suitable for efficient ion exchange operation. Such cellulosic exchanges are generally fibrous particulates which tend to become matted together during the operation of an ion exchange process, thereby plugging the column and greatly reducing the operating rates thereof. It has been proposed to employ the cellulosic exchanger in an agitated vessel to avoid this problem. However, this is not a wholly satisfactory solution to the problem because it would be more desirable to operate the ion exchange process in a conventional column operation. It has also been proposed to deposit the cellulosic exchanger on an inert, spheroidal support. However, this requires the use of a great volume of inert material in the ion exchange column, thereby increasing the size and cost of the necessary equipment.
U.S. Pat. Nos. 4,100,149 and 4,229,342 describe the use of porous silica coated with crosslinked ion exchange polymers to remove proteins from aqueous solutions. Unfortunately, such supported exchanges are quite expensive compared to conventional synthetic ion exchange resins.
The use of conventional vinyl aromatic ion exchange resins, e.g., functionalized styrene/divinylbenzene resins, to remove proteins from aqueous liquids have been said to be disadvantageous due to the excess of swelling of the resins, the tendency of the resins to foul, the tendency for proteins to become irreversibly attached thereto and an overall failure to perform adequately. Accordingly, such poly(vinyl aromatic) exchangers have not heretofore been proposed for use in separating compounds of animal waste streams
U.S. Pat. No. 3,969,538 describes the use of gel-type polystyrene sulfonate ion exchange resins to separate low molecular weight organic compounds from salts and organic molecules such as enzymes and proteins. While this process does provide a method for obtaining small organic compounds which are somewhat free from enzymes and salts, the separation is not as clean as desired and significant amounts of said enzymes and salts are found in the recovered low molecular weight organic compounds. In addition, this process does not provide a comprehensive process for separating all the material from animal or food waste streams into separate highly purified components.
Accordingly, it would be desirable to provide a process whereby the variable components of animal fluid waste streams are recovered in high purity preferably using inexpensive, commercially available ion exchange materials.